Height Of Hypertrophic Zone Research Articles

Growth deficiency in a mouse model of Kabuki syndrome 2 bears mechanistic similarities to Kabuki syndrome 1.

Growth deficiency is a characteristic feature of both Kabuki syndrome 1 (KS1) and Kabuki syndrome 2 (KS2), Mendelian disorders of the epigenetic machinery with similar phenotypes but distinct genetic etiologies. We previously described skeletal growth deficiency in a mouse model of KS1 and further established that a Kmt2d-/- chondrocyte model of KS1 exhibits precocious differentiation. Here we characterized growth deficiency in a mouse model of KS2, Kdm6atm1d/+. We show that Kdm6atm1d/+ mice have decreased femur and tibia length compared to controls and exhibit abnormalities in cortical and trabecular bone structure. Kdm6atm1d/+ growth plates are also shorter, due to decreases in hypertrophic chondrocyte size and hypertrophic zone height. Given these disturbances in the growth plate, we generated Kdm6a-/- chondrogenic cell lines. Similar to our prior in vitro model of KS1, we found that Kdm6a-/- cells undergo premature, enhanced differentiation towards chondrocytes compared to Kdm6a+/+ controls. RNA-seq showed that Kdm6a-/- cells have a distinct transcriptomic profile that indicates dysregulation of cartilage development. Finally, we performed RNA-seq simultaneously on Kmt2d-/-, Kdm6a-/-, and control lines at Days 7 and 14 of differentiation. This revealed surprising resemblance in gene expression between Kmt2d-/- and Kdm6a-/- at both time points and indicates that the similarity in phenotype between KS1 and KS2 also exists at the transcriptional level.

Analysis of Association between Morphometric Parameters of Growth Plate and Bone Growth of Tibia in Mice and Humans.

The purposes of this study are to evaluate which growth plate parameters are associated with bone growth in mice and to compare the mouse results with those in humans. The sagittal sections of the proximal growth plate of the mouse tibia from neonate to young adult stages were subjected to histomorphometric and functional analyses. The radiographic images of tibias of human patients until puberty were analyzed to obtain the tibia length and the proximal growth plate height. It was found that a linear correlation best modeled the relationship between the growth plate variables with the tibia growth rate and length. In mice, total height, resting zone height, combined height of the proliferation and prehypertrophic zones, proliferation activity, and the total width of tibia growth plate showed high linear correlation with tibia bone length and bone growth rate, but the hypertrophic zone height and the growth plate area did not. In both mice and humans, the total growth plate width of tibia was found to have the strongest correlation with tibia length and growth rate. The results validated that growth plate total height, the height of the resting zone and cell proliferation activity are appropriate parameters to evaluate the balance between growth plate activity and bone growth in mice, consistent with previous reports. The study also provided a new growth plate parameter candidate, growth plate width for growth plate activity evaluation in both mouse and human tibia bone.

Radial Extracorporeal Shock Wave Treatment Promotes Bone Growth and Chondrogenesis in Cultured Fetal Rat Metatarsal Bones.

Substantial evidence exists to show the positive effects of radialextracorporeal shock wave therapy (ESWT) on bone formation. However, it is unknown whether rESWT can act locally at the growth plate level to stimulate linear bone growth. One way to achieve this is to stimulate chondrogenesis in the growth plate without depending on circulating systemic growth factors. We wished to see whether rESWT would stimulate metatarsal rat growth plates in the absence of vascularity and associated systemic growth factors. To study the direct effects of rESWT on growth plate chondrogenesis, we asked: (1) Does rESWT stimulate longitudinal bone growth of ex vivo cultured bones? (2) Does rESWT cause any morphological changes in the growth plate? (3) Does rESWT locally activate proteins specific to growth plate chondrogenesis? Metatarsal bones from rat fetuses were untreated (controls: n = 15) or exposed to a single application of rESWT at a low dose (500 impulses, 5 Hz, 90 mJ; n = 15), mid-dose (500 impulses, 5 Hz, 120 mJ; n = 14) or high dose (500 impulses, 10 Hz, 180 mJ; n = 34) and cultured for 14 days. Bone lengths were measured on Days 0, 4, 7, and 14. After 14 days of culturing, growth plate morphology was assessed with a histomorphometric analysis in which hypertrophic cell size (> 7 µm) and hypertrophic zone height were measured (n = 6 bones each). Immunostaining for specific regulatory proteins involved in chondrogenesis and corresponding staining were quantitated digitally by a single observer using the automated threshold method in ImageJ software (n = 6 bones per group). A p value < 0.05 indicated a significant difference. The bone length in the high-dose rESWT group was increased compared with that in untreated controls (4.46 mm ± 0.75 mm; 95% confidence interval, 3.28-3.71 and control: 3.50 mm ± 0.38 mm; 95% CI, 4.19-4.72; p = 0.01). Mechanistic studies of the growth plate's cartilage revealed that high-dose rESWT increased the number of proliferative chondrocytes compared with untreated control bones (1363 ± 393 immunopositive cells per bone and 500 ± 413 immunopositive cells per bone, respectively; p = 0.04) and increased the diameter of hypertrophic chondrocytes (18 ± 3 µm and 13 ± 3 µm, respectively; p < 0.001). This was accompanied by activation of insulin-like growth factor-1 (1015 ± 322 immunopositive cells per bone and 270 ± 121 immunopositive cells per bone, respectively; p = 0.043) and nuclear factor-kappa beta signaling (1029 ± 262 immunopositive cells per bone and 350 ± 60 immunopositive cells per bone, respectively; p = 0.01) and increased levels of the anti-apoptotic proteins B-cell lymphoma 2 (718 ± 86 immunopositive cells per bone and 35 ± 11 immunopositive cells per bone, respectively; p < 0.001) and B-cell lymphoma-extra-large (107 ± 7 immunopositive cells per bone and 34 ± 6 immunopositive cells per bone, respectively; p < 0.001). In a model of cultured fetal rat metatarsals, rESWT increased longitudinal bone growth by locally inducing chondrogenesis. To verify whether rESWT can also stimulate bone growth in the presence of systemic circulatory factors, further studies are needed. This preclinical proof-of-concept study shows that high-dose rESWT can stimulate longitudinal bone growth and growth plate chondrogenesis in cultured fetal rat metatarsal bones. A confirmatory in vivo study in skeletally immature animals must be performed before any clinical studies.

Scoliosis vertebral growth plate histomorphometry: Comparisons to controls, growth rates, and compressive stresses.

Scoliosis progression in skeletally immature patients depends on remaining growth. Relationships between vertebral growth plate histomorphometry, growth rates, and mechanical stresses have been reported in several animal studies. Hypertrophic zone heights and chondrocyte heights have been used to assess treatments that aim to modulate growth. The purpose of this study was to determine whether human vertebral physeal hypertrophic zone and cell heights differed between two groups: Severe scoliosis and autopsy controls. Severity was defined at time of surgical planning by curve magnitude and curve stiffness. Physeal samples were obtained from the convex side apex, and from the concave side when feasible. Histologic sections were prepared, and digital images were used to measure hypertrophic zone height, cell height, and cell width. Thirteen spinal deformity patients were included, mean curve magnitude 67° (±23). Etiologies were juvenile and adolescent idiopathic, congenital, neurofibromatosis, neuromuscular, and Marfan syndrome. Five age-matched autopsy specimens without scoliosis served as controls. Results were presented by etiology, then all convex scoliosis specimens were combined and compared to controls. Zone heights for scoliosis, convex side, and controls were 152 µm (±34) and 180 µm (±42) (p = 0.21), cell heights 8.5 µm (±1.1) and 12.8 µm (±1.2) (p < 0.0005), and cell widths 14.9 µm (±1.5) and 15.0 µm (±2.5), respectively. Human values were compared to published animal models and to a quantitative theory of a stress ̶ growth curve. This quantification of vertebral physeal structures in scoliosis may be expected to help assess theories of progression and potential treatments using growth modulation. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2450-2459, 2018.

Regulation of bone growth via ligand-specific activation of estrogen receptor alpha.

Estrogens are well known for their capacity to promote bone maturation and at high doses to induce growth plate closure and thereby stop further growth. High-dose estrogen treatment has therefore been used to limit growth in extremely tall girls. However, recent data suggest that this treatment may have severe side effects, including increased risk of cancer and reduced fertility. We hypothesized that estrogenic effects in bone are mediated via ERα signaling. Twelve-week-old ovariectomized female C57BL/6 mice were subcutaneously injected for 4 weeks with E2 or selective ERα (PPT) or ERβ (DPN) agonists. After killing, tibia and femur lengths were measured, and growth plate morphology was analyzed. E2- and PPT-treated mice had shorter tibiae and femur bones when compared to vehicle-treated controls, whereas animals treated with DPN had similar bone lengths compared to controls. Growth plate height and hypertrophic zone height were reduced in animals treated with E2 or PPT but not in those treated with DPN, supporting that the effect was mediated via ERα. Moreover, PCNA staining revealed suppressed proliferation of chondrocytes in the tibia growth plate in PPT- or E2-treated mice compared to controls. Our data show that estrogenic effects on bone growth and growth plate maturation are mainly mediated via ERα. Our findings may have direct implications for the development of new and more selective treatment modalities of extreme tall stature using selective estrogen receptor modulators that may have low side effects than high-dose E2 treatment.

Effects of Phlomis umbrosa Root on Longitudinal Bone Growth Rate in Adolescent Female Rats.

This study aimed to investigate the effects of Phlomis umbrosa root on bone growth and growth mediators in rats. Female adolescent rats were administered P. umbrosa extract, recombinant human growth hormone or vehicle for 10 days. Tetracycline was injected intraperitoneally to produce a glowing fluorescence band on the newly formed bone on day 8, and 5-bromo-2′-deoxyuridine was injected to label proliferating chondrocytes on days 8–10. To assess possible endocrine or autocrine/paracrine mechanisms, we evaluated insulin-like growth factor-1 (IGF-1), insulin-like growth factor binding protein-3 (IGFBP-3) or bone morphogenetic protein-2 (BMP-2) in response to P. umbrosa administration in either growth plate or serum. Oral administration of P. umbrosa significantly increased longitudinal bone growth rate, height of hypertrophic zone and chondrocyte proliferation of the proximal tibial growth plate. P. umbrosa also increased serum IGFBP-3 levels and upregulated the expressions of IGF-1 and BMP-2 in growth plate. In conclusion, P. umbrosa increases longitudinal bone growth rate by stimulating proliferation and hypertrophy of chondrocyte with the increment of circulating IGFBP-3. Regarding the immunohistochemical study, the effect of P. umbrosa may also be attributable to upregulation of local IGF-1 and BMP-2 expressions in the growth plate, which can be considered as a GH dependent autocrine/paracrine pathway.

Peripubertal Caffeine Exposure Impairs Longitudinal Bone Growth in Immature Male Rats in a Dose- and Time-Dependent Manner.

This study investigated the dose- and time-dependent effects of caffeine consumption throughout puberty in peripubertal rats. A total of 85 male SD rats were randomly divided into four groups: control and caffeine-fed groups with 20, 60, or 120 mg/kg/day through oral gavage for 10, 20, 30, or 40 days. Caffeine decreased body weight gain and food consumption in a dose- and time-dependent manner, accompanied by a reduction in muscle and body fat. In addition, it caused a shortening and lightening of leg bones and spinal column. The total height of the growth plate decreased sharply at 40 days in the controls, but not in the caffeine-fed groups, and the height of hypertrophic zone in the caffeine-fed groups was lower than in the control. Caffeine increased the height of the secondary spongiosa, whereas parameters related to bone formation, such as bone area ratio, thickness and number of trabeculae, and bone perimeter, were significantly reduced. Furthermore, serum levels of IGF-1, estradiol, and testosterone were also reduced by the dose of caffeine exposure. Our results demonstrate that caffeine consumption can dose- and time-dependently inhibit longitudinal bone growth in immature male rats, possibly by blocking the physiologic changes in body composition and hormones relevant to bone growth.

Evaluation of varying levels of acid-binding capacity of diets formulated with various acidifiers on physical and histological characteristics of leg bones in broiler chickens

An experiment was conducted to investigate the effect of acid-binding capacity (ABC) and acidifiers in different basal diets on leg bones of broilers at 21 and 41 days of age. In a 3 × 2 × 2 factorial experiment, three levels of ABC (650, 800, and 950 mEq/kg), two mixes of acidifiers (fumaric acid and sodium diacetate and tartaric acid and calcium propionate), and two types of basal diet (optimal diet based on corn and suboptimal diet based on wheat–corn without enzyme) were assessed. Wheat–corn diet containing 650 mEq/kg ABC and tartaric acid caused the most density of femur, but fumaric acid resulted in the lowest density as compared with the other treatments at 21 days. The combination of fumaric acid and calcium carbonate improved bone density and ash percentage of tibia at 21 days. Tibia of chickens fed corn diet containing 650 mEq/kg ABC and fumaric acid had the highest density but with tartaric acid had the lowest density as compared with the other dietary treatments. However, the main effects and their interactions were not pronounced on weight, volume, and length of tibia at 21 days. Wheat–corn diet and 950 mEq/kg ABC significantly decreased phosphorus content of serum. However, the other factors and their interactions did not affect the phosphorus and calcium content of serum at 41 days. In histological traits of tibia, corn diet as compared with wheat–corn diet increased the height of proliferative zone but did not affect the hypertrophic and mineralized zones at 21 days. Tartaric acid as compared with fumaric acid significantly increased hypertrophic and mineralized zones but did not affect the proliferative zone at 21 days. The ABC at the level of 950 mEq/kg ABC significantly increased the height of hypertrophic zone but decreased proliferative and mineralized zones at 21 days. These factors and their interactions did not affect any zones of growth plate of tibia at 41 days.

The Increase in O-Linked N-Acetylglucosamine Protein Modification Stimulates Chondrogenic Differentiation Both in Vitro and in Vivo

Insulin is an inducer of chondrocyte hypertrophy and growth plate chondrogenesis, although the specific molecular mechanisms behind these effects are mostly unknown. Our aim was to investigate whether insulin-induced chondrocyte hypertrophy occurs through a modification in the amount of O-linked N-acetylglucosamine (O-GlcNAc)-modified proteins and in the expression of the key enzymes of this pathway, O-GlcNAc transferase and O-GlcNAcase (OGA). We also studied if O-GlcNAc accumulation per se, induced by an OGA inhibitor, was able to induce pre-hypertrophic chondrocyte differentiation both in vitro and in vivo. Insulin-induced differentiation of ATDC5 pre-chondrocytes occurred alongside a gradual increase in the accumulation of O-GlcNac-modified proteins (O-GlcNAcylated proteins), as well as an increase in the expression of O-GlcNAc transferase and OGA. In the absence of insulin, O-GlcNAc accumulation induced by thiamet-G, a specific OGA inhibitor, was able to increase the gene expression of differentiation markers, as well as the activity of MMP-2 and -9. Thiamet-G also activated pERK, p-JNK, and p-p38 and the O-GlcNAcylation of Akt. Thiamet-G administration to C57/bl mice induced a significant expansion in the growth plate height and in the hypertrophic zone height. Therefore, our results show that O-GlcNAc glycosylation has chondromodulating activity.

Impact of Unilateral Corrective Tethering on the Histology of the Growth Plate in an Established Porcine Model for Thoracic Scoliosis

Histological growth plate analysis. OBJECTIVE.: To evaluate the histological effects on vertebral growth plates following corrective mechanical tethering in the porcine scoliosis model. Theoretically, growth modulation allows progressive vertebral correction in the setting of scoliosis (Hueter-Volkmann principle). This IACUC-approved study divided 9 immature Yorkshire pigs into 2 groups: deforming tether release (TR, n = 4) group and anterior corrective (AC, n = 5) tether group. Once 50° coronal Cobb was demonstrated, TR had release of the deforming tether, whereas AC had release of the deforming tether and additional placement of a corrective tether. After 20 weeks of observation, pigs were killed, spines were removed, and apical samples were prepared for histological study. Growth plate analysis included the following histological parameters: proliferative zone height, hypertrophic zone height, and cell heights within the hypertrophic zone. Student t test was used to evaluate differences within and between groups. No significant differences were found within the release group on the concave versus convex side in terms of proliferative zone height, hypertrophic zone height, and cell heights in the hypertrophic zone. In the anterior correction group, the proliferative zone height was significantly smaller on the concave side than on the convex side (P < 0.01); no significant differences were found in AC on the concave versus convex side in terms of hypertrophic zone height and cell heights in the hypertrophic zone. No significant differences were found in any parameters between TR and AC on either the concave or the convex side. No significant decrease in any of the measured parameters was observed in the anterior correction group compared with the tether release group. These histological findings are consistent with preservation of growth potential.

The modulation of spinal growth with nitinol intervertebral stapling in an established swine model

Anterior spinal stapling for the treatment of adolescent idiopathic scoliosis has been shown to slow progression in small curves; however, its role in larger curves remains unclear. The purpose of this study was to evaluate the effectiveness of nitinol staples to modulate spinal growth by evaluating the two-dimensional and three-dimensional morphological and histological effects of this method in a well-established porcine model. Three immature Yucatan miniature pigs underwent intervertebral stapling. Two staples spanned each of three consecutive mid-thoracic discs and epiphyses. Monthly radiographs were obtained. Computed tomography (CT) was conducted at harvest after 6months of growth. Measurements of wedging and height for each disc and vertebral body were conducted. Micro CT was used to compare physeal closure between stapled and non-stapled levels. Histology of the growth plate also compared the hypertrophic zone thickness for control and stapled vertebrae. After 6months of stapled growth, the average coronal Cobb angle of the stapled segments increased by 7.7±2.0° and kyphosis increased by 3.3±0.6° compared to preoperative curves. Increased vertebral wedging and decreased disc height (p<0.001) were noted in stapled regions. Overall, 26±23% of each growth plate was closed in the stapled segments, with 6±8% closure in the unstapled levels. No difference was observed regarding the hypertrophic zone height when comparing instrumented to uninstrumented levels, nor was a difference recognized when comparing right versus left regions within stapled levels alone. Six months of nitinol intervertebral stapling created a mild coronal and sagittal deformity associated with reduced vertebral and disc height, and increased coronal vertebral and sagittal disc wedging.

Possible chondroregulatory role of prolactin on the tibial growth plate of lactating rats

Besides calcium accretion in the cortical envelope, a marked increase in the length of long bone was observed in pregnant and lactating rats, and thus the growth plate change was anticipated. Since several bone changes, such as massive trabecular bone resorption in late lactation, were found to be prolactin (PRL)-dependent, PRL may also be responsible for the maternal bone elongation. Herein, we investigated the growth plate change and possible chondroregulatory roles of PRL in the tibiae of rats at mid-pregnancy until 15 days postweaning. We found that the tibial length of lactating rats was increased and was inversely correlated with the total growth plate height, as well as the heights of proliferating zone (PZ) and hypertrophic zone (HZ), but not the resting zone (RZ). Chondrocytes in all zones expressed PRL receptors as visualized by immunohistochemistry, suggesting that the growth plate cartilage was a target of PRL action. Further investigations in lactating rats treated with an inhibitor of pituitary PRL release, bromocriptine, with or without PRL supplement, revealed the PRL-induced decreases in total growth plate height and HZ height from early to late lactation. However, decreases in RZ and PZ heights were observed only in late and mid-lactation, respectively. Thus, this was the first report on the chondroregulatory action of PRL on the growth plate of long bone in lactating rats. The results provided better understanding of the maternal bone adaptation during lactation.

A key role for membrane transporter NKCC1 in mediating chondrocyte volume increase in the mammalian growth plate

The mechanisms that underlie growth plate chondrocyte volume increase and hence bone lengthening are poorly understood. Many cell types activate the Na-K-Cl cotransporter (NKCC) to bring about volume increase. We hypothesised that NKCC may be responsible for the volume expansion of hypertrophic chondrocytes. Metatarsals/metacarpals from 16 rat pups (P7) were incubated in the presence/absence of the specific NKCC inhibitor bumetanide and measurement of whole-bone lengths and histologic analysis of the growth plate were done after 24 hours. Fluorescent NKCC immunohistochemistry was visualised using a confocal laser scanning microscopy on seven rat tibial growth plates (P7). Microarray analysis was performed on mRNA isolated from proliferative and hypertrophic zone cells of tibial growth plates from five rats of each of three ages (P49/53/58). Exposure to bumetanide resulted in approximately 35% reduction (paired Student's t test, p < .05) of bone growth in a dose-dependent manner; histologic analysis showed that a reduction in hypertrophic zone height was responsible. Quantification of fluorescence immunohistochemistry revealed a significant (paired Student's t test, p < .05) change in NKCC from the intracellular space of proliferative cells to the cytosolic membrane of hypertrophic zone cells. Further, microarray analysis illustrated an increase in NKCC1 mRNA between proliferative and hypertrophic cells. The increase in NKCC1 mRNA in hypertrophic zone cells, its cellular localization, and reduced bone growth in the presence of the NKCC inhibitor bumetanide implicate NKCC in growth plate hypertrophic chondrocyte volume increase. Further investigation is warranted to determine the regulatory control of NKCC in the mammalian growth plate and the possible detrimental effect on bone growth with chronic exposure to loop diuretics. © 2010 American Society for Bone and Mineral Research.

Spinal Hemiepiphysiodesis Decreases the Size of Vertebral Growth Plate Hypertrophic Zone and Cells

Hemiepiphysiodesis is a potential method to treat idiopathic juvenile scoliosis early. The purpose of the present study was to investigate a mechanism of curve creation in the pig thoracic model of spinal hemiepiphysiodesis by determining whether the structure of the vertebral growth plate varied with distance from the stapled, concave side of the spine. The hypotheses were that the heights of the hypertrophic zone, hypertrophic cells, and disc would be decreased on the treated side of the treated level as compared with both an unstapled control level and the side opposite the staple. Custom spine staples were implanted into six midthoracic vertebrae in each of five skeletally immature pigs. After eight weeks, the spines were harvested and histological sections were prepared. Hypertrophic zone height, hypertrophic cell height and width, and disc height were measured at discrete coronal plane locations at stapled and unstapled thoracic levels. Differences between stapled and unstapled levels and locations were compared with use of mixed linear modeling for repeated measures, followed by regression models to determine growth plate intercept and slope across the plane by thoracic level. Zone height, cell height, and cell width were lowest on the stapled side of the stapled level, with significant differences in the overall statistical model (p < 0.02). Disc heights were significantly reduced (p < 0.0001) at the stapled levels across the coronal plane. Unilateral control of intervertebral joint motion decreased growth plate height, cell size, and disc height.

Histomorphometric Evidence of Growth Plate Recovery Potential after Fractionated Radiotherapy: AnIn VivoModel

This study evaluated the hypothesis that early growth plate radiorecovery is evident by growth rate, histomorphometric and immunohistochemical end points after exposure to clinically relevant fractionated radiation in vivo. Twenty-four weanling 5-week-old male Sprague-Dawley rats were randomized into eight groups. In each animal, the right distal femur and proximal tibia were exposed to five daily fractions of 3.5 Gy (17.5 Gy) with the left leg serving as a control. Rats were killed humanely at 7, 8, 9, 10, 11, 14, 15 and 16 days after the first day of radiation exposure. Quantitative end points calculated included individual zonal and overall growth plate heights, area matrix fraction, OTC-labeled growth rate, chondrocyte clone volume and numeric density, and BrdU immunohistochemical labeling for proliferative index. Transient postirradiation reductions occurred early and improved during observation for growth rate, proliferative indices, transitional/hypertrophic zone matrix area fraction, proliferative height, and clonal volume. Reserve and hypertrophic zone height remained increased during the period of observation. The current model, using a more clinically relevant fractionation scheme than used previously, shows early evidence of growth plate recovery and provides a model that can be used to correlate temporal changes in RNA and protein expression during the early period of growth plate recovery.

The effects of dynamic axial loading on the rat growth plate.

Longitudinal bone growth can be suppressed by compressive loading. In this study, we applied three different magnitudes (17, 8.5, and 4N) of compressive force to growing rat ulnas 10 minutes/day for 8 days and investigated the effects on the distal growth plate biology. Further, to investigate growth rate recovery after cessation of loading, we examined rats 7 days after the loading period. Longitudinal growth of the ulna was suppressed in a dose-dependent manner by applied compressive force. In the 17N group, the longitudinal mineralization rate (LMR) at the distal growth plate was suppressed completely by loading and did not recover. However, in the 8.5N and 4N groups, LMR suppression recovered in 1 week. In the 17N group, growth plate height and hypertrophic zone height were significantly greater than control; the number of hypertrophic chondrocytes was increased; and some traumatic changes such as cracks in the growth plate were found. In addition, 17N loading suppressed cartilage mineralization and capillary invasion beneath the growth plate, although the number of chondrocytes synthesizing vascular endothelial growth factor (VEGF) was increased. Our study shows longitudinal growth suppression caused by axial loading of the ulna, which is proportional to the magnitude of load. Only the largest load (17N) caused morphological changes in the distal growth plate cartilage. There was no association found between mineralization and type X collagen localization or capillary invasion and VEGF expression.

HISTOMORPHOMETRIC ANALYSIS OF THE EPIPHYSEAL GROWTH PLATE IN RATS AFTER PRENATAL ALCOHOL EXPOSURE

We studied the effect of prenatal alcohol exposure on growth in the proximal tibial growth plate in 0- and 15-day-old rats, using histomorphometric methods. Body weight and tibial length were reduced in all alcohol-exposed rats. In 15-day-old rats, these parameters were lower than in the 15-day-old controls, thus showing a persistence of the effects of ethanol. The proximal tibial growth plate showed alterations, principally in 15-day-old rats. The most notable of these was a decrease in growth plate height produced by a significant reduction in hypertrophic zone height. Likewise, there were fewer cells in this zone in alcohol-exposed rats than in controls. This work shows that prenatal ethanol exposure induces growth retardation which may be due to growth plate alterations that might reflect impaired cell function.